1. Field of the Invention
The present invention relates to a liquid container which can contain various liquids and an apparatus in which the liquid container is mountable. In particular, the present invention relates to a liquid container which is preferably used as an ink tank containing pigment ink, and an apparatus in which the liquid container is mountable and which is preferably used as a printing apparatus for printing images using the pigment ink fed from the ink tank.
2. Description of the Related Art
For example, an ink tank as a liquid container containing ink is mounted in an ink jet printing apparatus or the like to supply ink to a print head provided in the printing apparatus. As examples of such an ink tank, Japanese Patent Laid-Open Nos. 2007-130812 and 2006-15694 describe ink tanks including a detection mechanism which detects when no ink remains in the ink tank.
The ink tank described in Japanese Patent Laid-Open No. 2007-130812 includes a flexible containing bag which contains ink and which is collapsed to pressurize the ink in the containing bag to supply the ink to the exterior though a supply port. A diaphragm is provided in an ink supply path which is in communication with the supply port. When the printing apparatus is supplied with ink through the ink supply path, the pressure in the ink supply path deforms and swells the diaphragm. On the other hand, when no ink remains in the containing bag, no ink is supplied through the ink supply path. Thus, the pressure in the ink supply path decreases to recover the diaphragm to its original shape. Such deformation of the diaphragm is utilized to detect the presence or absence of ink remaining in the containing bag.
The ink tank described in Japanese Patent Laid-Open No. 2006-15694 includes a flexible containing bag which contains ink and which is collapsed to pressurize the ink in the containing bag to supply the ink to the exterior though a supply port. The inside of the containing bag is in communication with one end of a communication pipe in which a gel-like follower is provided. The other end of the communication pipe is in communication with the atmosphere through a differential-pressure check valve. As the ink in the containing bag is supplied to the printing apparatus, the differential-pressure check valve is opened and closed so as to keep the difference in pressure between the inside of the containing bag and the outside air within a predetermined range. Thus, the position of the gel-like follower in the communication pipe is kept within a given range. When no ink remains in the containing bag, the differential-pressure check valve remains open, and the gel-like follower in the communication path moves out of the given range. Such movement of the gel-like follower is utilized to detect the presence or absence of remaining ink. A communication pipe formed of a transparent member allows the position of the follower, which corresponds to the remaining amount of ink, to be externally checked.
The ink tank described in Japanese Patent Laid-Open No. 2007-130812 allows the presence or absence of remaining ink to be detected utilizing a rise in ink pressure occurring when ink is pressurized and supplied. Consequently, this ink tank requires continued pressurization of the ink containing bag. If the pressurization is stopped, the diaphragm recovers to its original shape. Thus, to allow the presence or absence of remaining ink to be detected, a source of compressed air or the like for pressurization of the containing bag needs to be powered on to continue supplying compressed air. Furthermore, when the source is reactivated, the presence or absence of remaining ink cannot be detected until the containing bag is sufficiently pressurized.
The ink tank described in Japanese Patent Laid-Open No. 2006-15694 includes a complicated mechanism for detecting the presence or absence of remaining ink. This may lead to problems depending on the accuracy of components of the differential-pressure check valve. For example, if the inside of the communication pipe between the gel-like follower and the differential-pressure check valve is kept at a pressure higher than the atmospheric pressure by at least an acceptable value, when the pressurization of the ink containing bag is stopped, the gel-like follower moves a long distance, possibly causing erroneous detection of the “absence” of remaining ink. Furthermore, if the inside of the communication pipe between the gel-like follower and the differential-pressure check valve is kept at a negative pressure, when the ink tank with no ink remaining therein is removed, the outside air may flow into the containing bag through the ink supply port to move the gel-like follower. In this case, the “presence” of remaining ink is erroneously detected.